OTN is a protocol standard that is used for carrying multiple client signals or data streams on optical fibers over long distances with carrier-grade operations, administration, and management (OAM) functionality. OTN offers Time Division Multiplex (TDM) functionality that allows many independent client signals or data streams to be mapped and multiplexed into a higher-rate bit stream and then allows the higher-rate bit stream to be de-multiplexed and de-mapped back into the original independent client signals or data streams with low bit error rate and high fidelity transfer of frequency and phase of the client signals or data streams. The ability to carry more than one client signal or data stream within each OTN stream reduces the number of optical wavelengths or optical fibres required to physically connect all client signal or data stream sources to their destinations. OTN's Forward Error Correction (FEC) operations add at least 6 dB of signal enhancement to the client, facilitating transmission over long distances or facilitating a reduction in the number of optical amplifiers needed. OTN's OAM operations enable communication connections to be properly set up and configured, errors to be monitored, counted, and located, and protection switching to be triggered under failure conditions.
OTN devices introduce asymmetric delay when carrying multiple client signals or data streams. The introduction of asymmetric delay renders OTN devices using the known OTN protocol standard incapable of carrying two-way symmetric client signals or data streams, such as those described in Institute of Electrical and Electronics Engineers (IEEE) 1588 and the Common Public Radio Interface (CPRI) standards.
Improvements to OTN devices using the OTN protocol standard to facilitate the transport of two-way symmetric client signals or data steams over an OTN are therefore desirable.